Optical Measurements of the Electric Field of Pulsed Streamer Discharge in Water

We investigated the electric field of a streamer tip of pulsed streamer discharge in water by an optical measuring method. A crossed polarizer was used for the measuring of the electric field. The crossed polarizer is a conventional method to measure the electric field by Kerr effect. The crossed polarizer was composed by two polarizers. The first and second polarizers were set at the angle of 45deg and -45deg for beam polarization. These polarizers were set at both sides of an electrode. A He-Ne laser was used for the beam source. The electrode for generating the streamer discharge was pin and plane electrode in distilled water. The pulse of 53 kV of peak voltage with 300 ns width was applied to the pin electrode by Blumlein circuit. The electric field is obtained from the intensity of the laser beam going through the second polarizer by Kerr effect. The beam intensity was recorded by a high-speed camera with exposure time of 100 ns. An image of electric field was observed as the beam intensity away from the pin electrode when the streamer discharge arose. From that intensity, the average electric field of streamer tip was 400 kV/cm.